1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine or a printer, and to a cartridge that can be attached to an apparatus main body of such an image forming apparatus.
2. Description of the Related Art
Examples of the image forming apparatus include an electrophotographic image forming apparatus configured to form an image on a recording medium by using, for example, electrophotography. Examples of the electrophotographic image forming apparatus include an electrophotographic copying machine, an electrophotographic printer (e.g., a laser beam printer or a light-emitting diode (LED) printer), a facsimile apparatus, and a word processor.
In an electrophotographic image forming apparatus using electrophotography, such as a printer, an electrophotographic photosensitive member serving as an image bearing member (hereinafter referred to as a photosensitive drum) is uniformly charged, and a latent image is formed through selective exposure of the photosensitive drum. The latent image is developed with developer (hereinafter referred to as toner), and is made visible as a toner image. Then, the toner image is transferred to the recording medium.
By applying heat and pressure to the transferred toner image, the toner image is fixed to the recording medium, thus recording the image. Conventionally, such an image forming apparatus has involved maintenance of various process units.
As a means for facilitating this maintenance, there is adopted a cartridge system in which a photosensitive drum, a charging unit, a developing unit, a cleaning unit, etc., are all or partially integrated into a cartridge. In this system, the cartridge is attachable and detachable to and from an electrophotographic image forming apparatus.
In this cartridge system, it is possible for the user to perform maintenance on the apparatus by replacing the cartridge, so that it is possible to achieve a substantial improvement in terms of operability. Thus, this cartridge system is widely used in image forming apparatuses.
An image forming apparatus configured to form a color image, for example, is equipped with a plurality of cartridges. As a means for attaching and detaching the plurality of cartridges to and from the apparatus main body of the image forming apparatus, there is available a method which employs a moving member movable with respect to the apparatus main body, that is, a cartridge tray. The cartridge tray can move between the exterior and the interior of the apparatus main body with a plurality of cartridges placed thereon. By moving the cartridge tray to the interior of the apparatus main body with the cartridges placed on the cartridge tray, it is possible to attach the cartridges to the apparatus main body (Japanese Patent Application Laid-Open No. 2007-213024).
An example of the cartridge is formed by a cleaning frame member retaining a photosensitive drum, a charging unit, and a cleaning unit, a developing frame member retaining a developing unit, etc. The cleaning frame member has a waste toner accommodating portion configured to recover any toner adhering to the photosensitive drum without being used for image formation and to retain this waste toner. The developing frame member has a developer accommodating portion configured to accommodate toner to be carried by a developing unit (developing roller).
When, at the time of replacement of a cartridge, the user strongly grasps the cleaning frame member and the developing frame member constituting the cartridge, the inner pressure of the waste toner accommodating portion and of the developer accommodating portion increases, so that there is a fear of toner being scattered from within the cartridge.
Further, in the cartridge, in order to stabilize the quality of each process unit and to achieve an improvement in terms of their performance, it is necessary to perform high precision positioning on the components of each process unit and to maintain the positional relationship thus established until the end of their service life.
For the above reason, it is desirable that the cleaning frame member and the developing frame member exhibit high rigidity so that they may not undergo deformation.
Japanese Patent Application Laid-Open No. 2007-164094 proposes a cartridge whose frame members are provided with raised and recessed portions in order to mitigate the stress acting on the frame members due to temperature change during the transportation, storage, and use of the cartridge, thereby suppressing deformation of the frame members.
Generally, by providing the frame members of a cartridge with raised and recessed shapes, it is possible to enhance the rigidity thereof. However, when, as in the case of Japanese Patent Application Laid-Open No. 2007-164094, an attempt is made to arrange a plurality of cartridges in the apparatus main body of the image forming apparatus, there is the possibility of the raised and recessed shapes provided on the cartridges being allowed to interfere with each other. It might be possible to avoid this by enlarging the space provided inside the apparatus main body as the cartridge attachment portion and spacing the adjacent raised and recessed portions away from each other so that they may not interfere with each other. However, this would result in an increase in size of the image forming apparatus.
In particular, when a plurality of cartridges is attached to the apparatus main body of the image forming apparatus while placed on a cartridge tray (moving member), the size of the cartridge tray must also be increased. In this case, a large force and space may be required in order to move the cartridge tray.